Types of Circuit Elements

TYPES OF CIRCUIT ELEMENTS

Circuit element can be classified in many aspects.

Passive element

An element which receives energy (or absorbs energy) is called a passive element. They dissipate (in the form of heat) or store energy in an electric and magnetic field. Examples; resistor, inductor, capacitor, etc.

Active element

An element that supplies energy to the circuit is called an active element. Examples of active elements include voltage and current sources, generators, and electronic devices that require power supplies.

Bilateral element

An element which conducts current in both directions is called a bilateral element. Example resistor, inductor and capacitor.

Unilateral element

An element or a device in which current conduction is possible only in one direction is called unilateral element. Example: diode.

1. Passive circuit elements

There are three passive circuit elements. They are (a) Resistor, (b) Capacitor, (c) Inductor.

(1) Resistance

Electric resistance is the property of a material by which it opposes the flow of current. Energy is dissipated across a resistor in the form of heat. Resistance is denoted by R and the and the unit of resistance is ohm (Ω).

The resistance of a conductor

● is directly proportional to its length li.e.,

R ∝ 1

● is inversely proportional to area of cross section i.e.,

R ∝ l / a

● depends on the nature of conductor.

● Depends on temperature,

From these,

R ∝ ρl / a

where, ρ is a constant and is called resistivity or specific resistance. Its value depends on the nature of the material. Its unit is ohm-m. Specific resistance may be defined as the resistance offered by unit cube of the material between its opposite faces.

ρ ∝ Rl / a

(2) Capacitance

Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. The most common form of charge storage device is a two-plate capacitor.

Capacitor: A capacitor is an electrical device that can store energy in the electric field between a pair of closely-spaced conductors. When current is applied to the capacitor, electric charges of equal magnitude, but opposite polarity, build up on each conductor.

Capacitors are occasionally referred to as condensers.

(3) Inductance

Inductance is the property by virtue of which a circuit opposes the changes in the value of a time-varying current flowing through it. Inductance causes opposition only to varying currents and does not cause any opposition to steady or direct current. 

Inductor is the element in which energy is stored in the form of electromagnetic field.

2. Network elements

Loop (or) Mesh :

A loop or mesh denote a closed path obtained by starting at a node and returning back to the same node through a set of connected circuit elements without passing through any intermediate node more than once.

Node :

A node is a point in a circuit where two or more circuit elements join. A node is said to be an essential node if it joins three or more elements.

Branch:

A branch is a path that connects two nodes. Those paths that connect essential nodes without passing through an essential node are known as essential branches.